Systems and Methods for Gas Turbine Combustors

ABSTRACT

A gas turbine system includes a compressor operative to output an airstream and a diffuser having an inlet to receive the airstream and an outlet to output the airstream. The outlet has an area larger than the inlet to diffuse the airstream. The gas turbine system also includes a fuel nozzle operative to receive fuel and emit the fuel in a combustor and at least one bleed duct having an inlet between the compressor and the outlet of the diffuser. The at least one bleed duct is operative to direct bleed air from downstream of the compressor to the fuel nozzle.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to gas turbine combustorsand diffusers.

Gas turbines typically include a diffuser that decelerates the airemitted from the compressor prior to the air entering the combustor toreduce combustion system pressure loss and improve engine efficiency.Packaging considerations including engine size, weight, and cost oftenresult in the optimum diffusers having relatively short lengths. Somediffusers achieve a short length by bleeding air from the air streamnear the diffuser throat to energize the air flow near the diffuser walland prevent separation of the flow from the wall and aerodynamicinstability.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a gas turbine systemcomprising, a diffuser operative to diffuse an airstream output from acompressor, a fuel nozzle operative to receive fuel and emit the fuel ina combustor, and at least one bleed duct operative to direct bleed airfrom down stream of the combustor to the fuel nozzle.

According to another aspect of the invention, a method for routing bleedair comprises outputting an airstream of compressed air from acompressor, drawing bleed air from the airstream down stream from thecombustor, and directing the bleed air through a duct to a fuel nozzle.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification.

The foregoing and other features, and advantages of the invention areapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a side partially cut-away view of a portion of a gas turbineengine.

FIG. 2 is a front partially-cut away view of the gas turbine enginealong the line A-A of FIG. 1.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a side partially cut-away view of a portion of a gasturbine engine 100. The gas turbine engine 100 includes a compressorportion 102, an outer casing 104, a diffuser portion 106, a transitionpiece 108, an impingement sleeve 110, a mount portion 112 connected tothe outer casing 104, a bracket portion 114 connected to the mountportion 112, a head end volume 116 partially defined by the transitionpiece 108, a plurality of fuel nozzles 118 communicative with the headend volume 116, and a bleed air duct 120.

In operation, the compressor portion 102 compresses air in an airflowpath indicated by the arrow 101. The airflow path flows into thediffuser portion 106. The diffuser portion reduces the velocity of thecompressed air by increasing the cross-sectional area of the airflowpath. A portion of the compressed air contacts the impingement sleeve110 and flows along the outer surface of the transition piece 108. Theflow of air along the outer surface of the transition piece 108 coolsthe transition piece 108, and enters the head end volume 116.

The bleed air duct 120 draws bleed air from the airflow path via avortex cavity 122. The bled air increases the effectiveness of thediffuser portion 106 by improving the diffuser pressure-recoverycoefficient. The arrangement of the impingement sleeve 110 in theairflow path induces a low driving pressure that improves the ducting ofbleed air into the bleed air duct 120. The bleed air is routed into thehead end volume 116.

The bleed air and the transition piece 108 cooling air mix in the headend volume 116 and enters the fuel nozzles 118. The air mixes with fueland is discharged from the fuel nozzles 118 into the combustion chamber124 where the fuel air mixture is ignited. The arrangement provides thebleed extraction for boundary layer control and efficiency, low pressureloss operation of the diffuser, and routes the bleed air to the fuelnozzles upstream of the first turbine rotor stage. This arrangement andsequence allows the air to be used for premixing with fuel, lowering theemission of nitrogen oxides, and also avoids injection of the bleed airdownstream of the first turbine rotor, increasing output and efficiencyrelative to a downstream air return arrangement.

Routing the bleed air to the fuel nozzles increases the efficiency ofthe engine and decreases undesirable emissions since the air removedfrom the air stream is used in the combustion of fuel. Previous systemsand methods routed the bleed air down stream from the compressor, whichmay reduce output performance and efficiency and increase exhaustpollution levels.

The illustrated embodiment shows the bleed air duct 120 routed throughthe outer casing 104, the mount 112, and the bracket 114. The use of theouter casing 104, the mount 112, and the bracket 114 to define the bleedair duct 120 decreases the packaging area in the gas turbine 100.Alternate embodiments may include a second vortex cavity 126 that isoperative to draw additional bleed air, and rout the bleed air to thebleed air duct 120. Other alternate embodiments may include any numberof vortex cavities that draw bleed air into the bleed air duct 120.

FIG. 2 illustrates a front partially-cut away view of the gas turbineengine along the line A-A (of FIG. 1). FIG. 2 shows the bleed air duct120 partially defined by the bracket 114 having a Y-shape. The bracket114 supports the transition piece 108. Other embodiments may include abracket having a single bleed air duct 120 path as opposed to a Y-shapedduct.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

What is claimed is:
 1. A gas turbine system comprising: a compressoroperative to output an airstream; a diffuser having an inlet to receivethe airstream and an outlet to output the airstream, the outlet havingan area larger than the inlet to diffuse the airstream; a fuel nozzleoperative to receive fuel and emit the fuel in a combustor; and at leastone bleed duct having an inlet between the compressor and the outlet ofthe diffuser, the at least one bleed duct operative to direct bleed airfrom downstream of the compressor to the fuel nozzle.
 2. The system ofclaim 1, wherein the bleed duct includes a first vortex cavity at theinlet of the bleed duct operative to draw compressed air from the atleast one airstream in the diffuser.
 3. The system of claim 2, whereinthe system further comprises an outer casing that defines the diffuser,and the first vortex cavity is a recess in the outer casing.
 4. Thesystem of claim 2, wherein the first vortex cavity is located betweenthe inlet and the outlet of the diffuser.
 5. The system of claim 1,wherein the bleed duct includes a second vortex cavity operative to drawcompressed air from the at least one airstream.
 6. The system of claim1, wherein the system further comprises an outer casing that defines thediffuser, and the at least one bleed duct passes through the outercasing.
 7. The system of claim 1, wherein the fuel nozzle is partiallydisposed in a cavity, the cavity operative to receive the bleed air androut bleed air to the fuel nozzle.
 8. The system of claim 1, wherein thesystem further comprises an impingement sleeve operative to induce adriving pressure on the airstream.
 9. The system of claim 2, wherein thefirst vortex cavity is located up stream of the diffuser.
 10. The systemof claim 1, wherein the system comprises: an outer casing that definesthe diffuser; and a bracket mounted to the outer casing configured tosupport the combustor, the at least one bleed duct defined by a channelthrough the outer casing to the bracket, and through the bracket to thefuel nozzle.
 11. The system of claim 10, wherein the bracket is Y-shapedand defines a first flow path of the at least one bleed duct through thebase of the “Y” and one arm of the “Y.”
 12. The system of claim 11,wherein the bracket defines a second flow path of the at least one bleedduct through the other arm of the “Y.”
 13. The system of claim 1,wherein the system further comprises an outer casing that defines thediffuser, the at least one bleed duct passes through the outer casing tothe fuel nozzle, and the air flow flows out from the outlet of thediffuser to the fuel nozzle.
 14. A method for routing bleed aircomprising: outputting an airstream of compressed air from a compressor;diffusing the airstream in a diffuser; drawing bleed air from theairstream downstream from the compressor and upstream from an outlet ofthe diffuser; and directing the bleed air through a duct to a fuelnozzle.
 15. The method of claim 14, wherein the bleed air is drawn fromthe airstream with a first vortex cavity located upstream from thediffuser.
 16. The method of claim 14, wherein the bleed air is drawnfrom the airstream by a first vortex cavity located in the diffuser. 17.The method of claim 15, wherein air is drawn from the airstream by asecond vortex cavity located in the diffuser.
 18. The method of claim14, wherein a driving pressure is induced on the air stream by animpingement sleeve.
 19. The method of claim 14, further comprising:directing the airstream from the diffuser along an impingement sleeve tothe fuel nozzle.